Tube mills are used mainly for grinding materials such as ore. It is not unusual for the operation of a tube mill to be interrupted and the tube mill to be out of action for a relatively long period of time. This occurs for maintenance reasons, for example. During the standstill of the tube mill, the material present in the grinding pipe of the tube mill can consolidate and adhere firmly to the inner wall of the grinding pipe. Such firmly adhering, consolidated material stuck to the inner wall of the grinding pipe is referred to as frozen charge. When the tube mill is brought back into operation after a relatively long standstill, there is a risk that the frozen charge will become detached from the grinding pipe at great height, fall down and cause considerable damage to the tube mill when it then strikes the grinding pipe.
Arrangements therefore exist which detect the presence of frozen charges and, when the presence of a frozen charge is detected, switch the tube mill off. Such an arrangement is described in German laid-open print DE 35 28 409 A1, for example.
If a frozen charge is detected and the tube mill is switched off, the frozen charge must then be removed, which is laborious. This is done, for example, by softening, by water being sprayed onto the frozen charge and/or using compressed-air hammers. Removal of a frozen charge requires an extremely great, for the most part manual, expenditure of work and is very time-intensive.